Fluid blast circuit interrupter



April 1962 H. N. SCHNEIDER 3,028,465

FLUID BLAST CIRCUIT INTERRUPTER Filed Oct. 6, 1953 Fig.2.

WVllllllllfllllllllllllll"I"IllIIIIIIIIIIIIIIIIHIHIIW!IlllMIIIIHIIIIIIIIIW' LENGTH llIllllllllIIllllllllllllllllllllllllfiInventor:

Harold N. Schneider,

His Attorney United States Patent O 3,028,465 FLUID BLAST CIRCUITINTERRUPTER Harold N. Schneider, Springfield, Pa., assignor to GeneralElectric Company, a corporation of New York Filed Oct. 6, 1958, Ser. No.765,663 4 Claims. (0. 200-150) This invention relates to an electriccircuit interrupter and, more particularly, to an interrupter of thefluidblast type in which a circuit-interrupting arc is establishedwithin a body liquid contained with-inan arc-extinguishing unit.

When an arc is established within a body of liquid, the arc reacts withthe liquid to generate gases having a volume varying directly with themagnitude of the current interrupted. If the liquid is locatedinternally of an on closed arc-extinguishing unit and the currentinterrupted is of great magnitude, large quantities of the gasesgenerated must be rapidly vented from the unit in order to preventexcessive pressures from developing within the enclosure. For ventingsuch gases, it is customary to provide the unit with exhaust portsleading from the arcing region to the exterior of the unit. The areaavailable for these ports is limited by considerations such as the needfor avoiding excessive venting during the interruption of lower currentsand the mechanical strength of the walls of the enclosure. Hence, it isimportant that efficient use be made of the overall exhaust port areathat is available. Prior exhaust port arrangements of which I am awarehave not been as efficient as might be desired in allowing for ventingof these gases.

Accordingly, an object of'the present invention is to provide animproved exhaust port arrangement which is exceptionally efiicient inventing the relatively large volume of gases generated during heavycurrent interruptions.

To facilitate the interruption of high-current arcs, it is important, asa general rule, that the are be cooled as rapidly as possible. Thiscooling is accomplished in a fluid blast interrupter by drivingpressurized fluid through the arcing region. By utilizing this fluidflow to'best advantage, lower pressures may be relied upon within thearc-extinguishing unit for interrupting currents of a given value. Froma mechanical strength viewpoint, a lessening of internal pressures is,of course, desirable.

Accordingly, another object of my invention is to provide an exhaustport arrangement which lends itself to obtaining a near-maximum in arccooling effect from -a given amount of flow through the exhaust ports.

In carrying out my invention in one form, I arrange the exhaust ports insuch a manner that the venting areas provided along the length of atypical heavy current are, in efi'iect, match the gas-generationcharacteristics of the are. More particularly, in the region where thearc is hottest, i.e., centrally of its length, its gas-generatingability is the greatest, and it is in this central region that thelargest venting area is provided. At the arc terminals the arc isrelatively cool as compared to centrally thereof, and, accordingly, inthese regions, venting areas of lesser size than in the central regionare provided.

For a better understanding of my invention, reference may be had to thefollowing specification taken in conjunction with the accompanyingdrawing, wherein:

FIG. 1 is a side elevation-a1 view partially in section of a fluid-blastinterrupter embodying my invention.

FIG. 2 is an enlarged view taken along the line 2-2 of FIG. 1.

HS. 3 is a graphic representation of certain temperature characteristicsof a high current are.

FIG. 4 is a cross sectional view of a portion of a modified interrupterembodying my invention.

FIG. 5 is a cross sectional view taken along the line 5-5 of FIG. 4.

Referring now to FIG. 1, the interrupter shown therein is of the generaltype disclosed and claimed in Patent No. 2,749,412, McBride et a1.,assigned to the assignee of the present invention. This interrupter 1 ismounted along with another similar interrupter (not shown) inside arelatively large oil-filled enclosing tank. The two interrupters areelectrically connected by a reciprocable blade contact 2 of conventionalform, such as shown, for example, in U.S. Patent No.l.,548,799I-Iilliard, assigned to the assignee of the present invention.

7 The interrupter 1 is supported from the tank by means of insulatingbushing structure 3. The bushing structure The-interrupter 1 comprisesan insulating casing 5 enclosing a pair of separable interruptingcontacts which are electrically connected in the power circuit extendingfrom the adapter 4 through the interrupter. ,One of the contacts of thepair is a relatively fixed contact assembly 1% and the other is arelatively movable rod-type contact 11. The fixed contact assembly 10 ispreferably of the conventional cluste -type comprising aplurality offingers 12 circumferentially spaced about a conductive rod 14 integralwith the adapter 4. The fingers 12 are pivoted adjacent their upper endson the conductor 14 and arebiased radially inward by suitable resilientmeans (not shown). When the interrupter is in its closed position, themovable rod-type contact 11 is in its position of FIG. 1, where it isshown embraced by the radially-inwardly biased fingers 12 of thestationary contact assembly 10.

The movable rod-type contact 11 is supported on asuitable conductivecross-head 16 having an external contact button 17 projecting downwardlytherefrom. This contact button 17 cooperates with an isolating contact18 secured to the movable switch blade 2 to form a pair of isolatingcontacts.

A contact-opening operation is performed by driving the switch blade 2rapidly downward. This allows a suitable compression spring 19 to forcethe crosshead 16 together with movable rod contact 11 rapidly downwardto draw a circuit-interrupting arc in the region where the rod contact11 parts from the stationary contact assembly 10. After a predetermineddownward movement, the crosshead 16 is blocked by suitable stop means(not shown) from following the switch blade 2. The switch blade 2,however, continues moving downwardly and, as a result, establishes anisolating break between the contacts 17 and 18 in a well-known manner.

The above-described circuit-interrupting arc reacts with the surroundingoil inside the interrupter Ito create a blast of fluid through thearcing region, and this blast aids in extinguishing the are, as willsoon be described in greater detail.

For directing the fluid blast into the arcing region, anarc-extinguishing unit in the form of a ba'ille stack 20 is providedimmediately beneath the stationarycontact 10. This baffle stack 20 isformed of a plurality of superposed bafi'le plates 23 of insulatingmaterial, preferably of a circular configuration in planview. Thesebaflle plates 23 are clamped together and have registering aperturesprovided internally thereof so as to form a verticallyextending arcingpassageway 24 for receiving the vertically movable rod contact 11. Mostof the battle plates 23 are also slotted so as to provide flow passagesradiating from the arcing passage 24. The flow passages 25 located tothe right of the arcing passage 24 direct the fluid blast into thearcing region, whereas those passages 26 to the left of the arcingpassage 24 constitute exhaust passages for venting the arcing productsand the fluid blast from will be noted that certain of theintermediately-located bafile plates 23 are not provided with slots.Those edges of these plates which surround the arcing passage 24 serveas barriers for restraining the are within the arcing passage 24 so thatit is not driven through the exhaust passages 26 into the region outsidethe interrupter by the fluid blast.

The present invention is particularly concerned with the configurationof the exhaust passages 26, especially at the months, or outer ends,thereof. These outer ends are hereinafter referred to as exhaust portsand are designated 27a, 27b and 270. The slots forming the flow passages26 preferably have their minimum width at the exhaust ports, and, thus,the flow passages 26 are less restricted upstream from the exhaust portsthan they are at the exhaust ports. It will be noted that the casing Sis provided with an opening 28 that aligns with these exhaust ports toallow for escape of the arcing products into the surrounding oil. Theconfiguration of the exhaust ports 27a, 27b, and 270 is best illustratedin FIG. 2, which is an enlarged view taken from outside the interrupterlooking in the direction of exhaust ports. It will be noted from FIG. 2that the central exhaust port 27a hasa considerably larger area than theexhaust ports 27b and 270 located at vertically opposite sides thereof.This exhaust port configuration provides for highly etficient venting ofthe arcing products for reasons which will now be explained.

For the purposes of explanation it will be assumed that an are such asshown at 30 in FIG. 3 is established between a pair of contactscorresponding to the contacts and 11 of the interrupter of FIG. 1. Thetemperature of the arc taken at points along its length has a characteristic curve of the configuration shown immediately beneath the arc. Asindicated by the curve, the arc temperature is the highest centrally ofthe arc length and is of a considerably lesser value adjacent eachcontact or electrode. This is the case because vaporized electrodematerial, which is relatively cool compared to the temperature, of thearc plasma, cools the ends of the arc. Since the amount of gas generatedwhen the arc reacts with the surrounding oii'varies directly withtemperature, it will be apparent that more gas will be generated in thecentral region of the arc than at its ends. In other words, if thevolume of gas generated at particular points along the arc length wereto be plotted against arc length, then the resulting cunve would havegenerally the same character'i'stic shape as the temperature curveplotted in 7 FIG. 3.

To exhaust these generated gases in the most efiicient manner with agiven overall exhaust port area, I have concluded that the exhaust portarea configuration should substantially match the gas-generatingcharacteristics of the are. In other words, where the gas-generatingcapacity is the greatest, the greatest exhaust area should be provided,and where the gasgenerating capacity is the smallest, the smallestexhaust port area should be provided. This end is achieved in theinterrupter of the present invention by proportioning the exhaust portsso that the greatest venting area is located centrally of the arc lengthand venting areas of lesser size are located adjacent the ends of thearc. The arc length may, of course, vary for currents of difierentmagnitude, but the arc length that Should be used as a reference basefor positioning of the ports is the arc length at which maximumgas-generation will take place when interrupting currents near themaximum interrupting rating of the interrupter. This condition resultsat or slightly past the point of peak current preceding interruption.

It is recognized that for other arc lengths, e.g., the.

longer are lengths that would beencountered with lower currents, thearcing products would not be exhausted with the same high degree ofefficiency, but for such conditions,

the quantity of gases generated is relatively low, and, thus, 1

the same high degree of: eificiency is not necessary. 7

One might inquire as to whether it would be disadvantageous to make allthree of the exhaust ports of the same size as the centrally locatedexhaust port 27a. With regard to this inquiry, there are a number ofdisadvantages which would result from such an approach. First of all,

it the overall exhaust port area is increased appreciably 7 I Increasingthe size of opening 28 is disadvantageous because it tends tomechanically weaken the casing 5 and to thus impair the ability of thecasing 5 to withstand the high pressures encountered during extreme highcurrent V interruptions.

Another advantage thatthe disclosed exhaust port configuration has overone which utilizes exhaust ports of equal area and shape is that thedisclosed configuration provides for a more efiicient cooling of thearc. In this regard, in the particular region where the arc temperature.

is the highest, i.e., centrally of its length, the greatest amount offlow is provided, and in the regions where the arc temperature is theleast, i.e., at its ends, the least amount of flow is provided. Sincethe cooling that takes place at any region along the arc length isdependent upon the flow across that particular region, it will beapparent that distributing the flow in accordance with the arctemperature provides for flow commensurate with cooling requirements.Accordingly, there is no appreciable amount of flow wastefullydissipated adjacent the ends of the arc, and thus efiicient utilizationis made of the flow that is present. v

The fact that the cross-section of the arc is of a lesser size near itsends than centrally thereof is another factor which renders thedisclosed exhaust port arrangement highly efiicient from a coolingviewpoint. In this regard, the restricted nature of the end exhaustports causes the transverse flow adjacent the arc ends to be directedclosely adjacent the arc periphery rather than along some pathrelatively remote from the are where the .cooling efiect would be muchless pronounced. The ability toefiiciently utilize the available flowenables a lesser amount 7 of flow to be relied upon to perform the sameamount of cooling. If lesser flow is required, the pressures within theinterrupter which produce this flow may be of alesser value, Hence, byefficiently utilizing the flow, my exhaust port arrangement enableslesser pressures to be utilized for interrupting currents of a givenvalue than would be required with less efiicient flow patterns..Lessening of internal pressures is, of course, desirable from amechanical strength viewpoint.

To facilitate low currentinterruptions in, the interrupter of FIG. 1, aconventional impulse pump 40 is provided at the right hand side of theinterrupter casing 5. This pump comprises a piston 41 mounted forvertical movement inside a. cylinder 42 and biased by means of a com-'pression spring 44 tomove downwardly in response to opening of theinterrupter. While the interrupter is closed,

the piston 41 is maintained in its elevated position of FIG. 1 by meansof a plunger 45 secured to the switch blade 2 and abutting against thelower end of the piston rod. However, when the switch blade 2 is drivendownwardly to open the interrupter, the restraint of the plunger isremoved and the spring 44 is free to begin driving the piston 41downwardly against the opposition of the oil therebeneath.

When the piston moves downwardly, it tends to force liquid into the flowpassages 25 via a conventional check valve 43 interposed between thepump at} and the flow passages 25. The check valve43 comprises aslidably mounted valve element 43a which allows flow to take place onlyfrom the pump into the casing 5 and not in a reverse direction. Lowcurrent arcs generate within the interrupter relatively low pressureswhich are incapable of holding the check valve 43 closed, and, hence,the pump is capable of directing a flow through the passages under suchconditions. This flow aids in extinguishing low current arcs. Under highcurrent interrupting conditions, however, the pressure generated withinthe interrupter is higher than the pump pressure and forces the checkvalve 43 to remain closed until after the interruption is over. Uponcompletion of the interruption, the pressure within the interrupterquickly diminishes, and the pump then becomes operative to scavenge theinterrupter of arcing products. Impulse pumps such as are well-known,and reference may be had to the aforementioned McBride et al. patent fora more complete description of pump of this character.

A modified interrupter wherein the exhaust port configuration of thepresent invention has been found particularly advantageous isillustrated in FIG. 4. Here the arcing products, instead of being ventedfrom the exhaust ports 27a, 27b, 27c directly into the surrounding oil,are

vented through a pressure-responsive exhaust valve before entering thesurrounding oil. An exhaust valve of this character is shown and claimedin my application SN. 717,892, filed February 27, 1958, now Patent No.2,927,181, issued March 1, 1960, and assigned to the assignee of thepresent invention.

For the purposes of the present application, the following briefdescription of exhaust valve 50 is believed to be suificient. Referringto FIG. 4, it will be noted that the exhaust valve 50 comprises atubular valve body 51 suitably secured within an opening formed in thecasing 5. The securing means may be of any conventional form, butpreferably comprises a nut 57 and a shoulder 58 between which the wallof the casing 5 is clamped. Within the tubular valve body 51 is aflow-controlling vane 52 coupled to a pivotally mounted shaft 53. Atension spring 54 disposed about the outer periphery of the valve body51 acts through suitable cranks 55 coupled to the shaft 53 normally tobias the vane 52 into its closed position of FIG. 4. During low currentinterruptions, the pressure developed within the interrupter isrelatively low, and under such conditions the spring 54 holds the vane52 closed, thereby assuring that suflicient pressure will be built upinside the interrupter to enable low current arcs to be efficientlyextinguished. Under high current interruptions, large quantities of gasare generated within the interrupter, and accordingly relatively highpressures are built up therewithin. In response to such pressures, thevane 52 is forced open against spring 54 to allow the arcing products tobe vented from the interrupter, thereby preventing excessive pressurerises within the interrupter.

To avoid impairing the mechanical strength of interrupter casing 5, itis desirable that the valve body 5'1 be as small as possible. the valvebody 51 must be large enough to allow for a sufiicient flow of arcingproducts during extreme high current interruptions to prevent excessivepressures from being developed within the interrupter 1. The exhaustport arrangement of the present invention enables the valve body to beof a near-minimum size because the .thus enabling these products to berapidly exhausted before excessive pressures can be developed.

The exhaust ports in FIG. 5, like those in FIGS. 1 and 2, are positionedalong a length of the interrupter which is generally coextensive withthe arc length at which maximum gas-generation will take place wheninterrupting currents near the maximum rating of the interrupter. Alonga diameter of the .bore of valve body 51 extending lengthwise of theinterrupter, the central exhaust port 27a provides a larger venting areathan the exhaust ports 27!) and 270 near the terminal of the arc.

While I have shown and described particular embodiments of my invention,it will be obvious to those skilled in the art that various changes andmodifications may be made without departing from my invention in itsbroader aspects and I, therefore, intend in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. -In an electric circuit interrupter for interrupting currents up to apredetermined rated value, an enclosure containing a body of insulatingliquid and an arc-extinguishing unit immersed within said liquid, meansfor establishing within said unit circuit-interrupting arcs that areadapted to react with said insulating liqiud to gencrate a volume of gasdependent upon the current being As a limiting consideration, however,

sages having a region of maximum restriction defining an 1 exhaust portof fixed cross-sectional area in said exhaust passage, said ports beingdisposed along a length of said unit generally coextensive with saidpredetermined general length and providing centrally of said generallength a substantially larger venting area than at either end of saidgeneral length, those arcs that have a low current.

value in comparison to said rated value extending over saidpredetermined general length plus an, additional length of saidarc-extinguishing unit. 7

2. The interrupter of claim 1 in which said arc-extinguishing unit isconstructed of a plurality of superposed baflle plates stackedlengthwise of said unit, said bafile plates including slots extendingtransversely of the length of said arc-extinguishing unit to define saidexhaust passages, each of said exhaust pasages having its region ofmaximum restriction at its outer end to define one of said exhaustports, those slots located centrally of said general length beingsubstantially wider at said exhaust parts than those slots located ateither end of said general length.

3. In an electric circuit interrupter, an enclosure containinginsulating liquid and an arc-extinguishing unit immersed therein. saidarc-extinguishing unit having an arcing passage extending longitudinallyof said unit and longitudinally of said enclosure, means forestablishing within said arcing passage an are adapted to react withsaid insulating liquid to generate gases said arcing passage having apredetermined general length over which those arcs having a currentvaluue near the maximum rated current value of said interrupter extendat the instant of maximum gas generation, means for venting said gasesfrom said unit in a direction transverse to the length of said enclosurecomprising a plurality of exhaust passages in said arc-extinguishingunit extending transversely from said arcing passage to the exterior ofsaid unit for venting arc-generated gases therefrom, each of saidexhaust pasages having a region of maximum restriction defininganexhaust port of fixed cross-sectional area in said exhaust passage, saidexhaust ports providing a substantially larger venting area centrally ofsaid predetermined general length of said arcing passage than at eitherend of said predetermined general length of said arcing passage, thosearcs that have a low current value in comparison to said rated valueextending over said predetermined general length plus an additionallength of arcing passage.

4. In an electric circuit interrupter for interrupting currents up to apredetermined rated value, an enclosure containing a body of insulatingliquid and an arc-extinguishing unit immersed within said liquid andcontaining an arcing passage, means for establishing within said arcingpassage arcs that are adapted to react With said insulating liquid togenerate a volume of gases dependent upon the current being interrupted,those arcs that have a current value near said predetermined rated valueextending over a predetermined general length of said arcing passage atthe instant of maximum gas generation, means for venting said gases fromsaid unit comprising a plurality of exhaust passages extendingtransversely from said arcing passage to the exterior of said unitforventing aregenerated gases therefrom, each of said exhaust passageshaving a region of maximum restriction defining an exhaust port of fixedcross-sectional area in said exhaust passage, said exhaust ports beinglocated along said pre determined general length of said arcing passagein communication with said arcing passage, a valve body having agenerally circular flow passage extending therethrough, means forsupporting said valve body adjacent said arc extinguishing unit in aposition wherein said flow passage aligns with said plurality of portsand provides an outlet for fluid flowing through said ports, said portsbeinglo-.

cated along a diameter of said flow passage extending generally parallelto said arcing passage, said ports providing centrally of said diametera substantially larger venting area than at the opposite ends'of saiddiameter,

and pressure-responsive means for controlling flow through said flowpassage in accordance with the pressures developed within said unit as aresult of an interrupting operation, those arcs that have a low currentvalue in comparison to said rated value extending over saidpredetermined general length plus an additional length of said arcingpassage.

References Cited in the file of this patent UNITED STATES PATENTS

